Graphene and its precursor graphene oxide (“GO”) belong to the frontier of new materials having unique electrical, thermal, or even mechanical properties with wide application potentials. To date, contemporary graphene production involves chemical oxidation of graphite to graphite oxide or graphene oxide under high temperature and other extreme reaction conditions, followed by reducing GO to graphene using chemical, thermal, or even electrochemical methods. GO not only is an important precursor for mass production of graphene-based materials, it may also have great potentials to be used in many areas, such as but not limited to, electronics, optoelectronics, bio-nanotechnology, renewable energy, membrane research, environmental applications, or the like. In the past, GO has been mainly synthesized by chemical oxidation based on the Hummers, Brodie, or even Staudenmaier methods. All of these chemical methods use concentrated acids, such as sulfuric acid (H2SO4) and nitric acid (HNO3), or even toxic reagents, such as potassium dichromate (K2Cr2O7), potassium permanganate (KMnO4), or even explosive potassium chlorate (KClO3) to oxidize graphite to GO, and the production procedure can be expensive, dangerous, and even non-sustainable.
Certain electrochemical exfoliation of graphite to GO or graphene has been attempted in ionic liquids such as aqueous acids and inorganic salt solutions under between about 7V to about 20V in voltage, and the products were reported with different levels of defects in the crystal lattice and even oxygen-doping. Certain biological methods have also been attempted and reports show that microorganisms can oxide dispersed graphite to graphite oxide nanosheets, but external carbon sources and oxygen were needed and the reaction rate was too low to have commercial value.
It is thus a need to provide new systems and methods which can produce graphene or GO at rates of commercial merit, under ambient conditions, under mild conditions, or the like.